It is known that heat curable workable foundry molds and cores can be prepared by the so-called "hot-box" process. This process involves injecting a foundry mix consisting of a foundry aggregate containing a latent acid curing catalyst and a thermosetting resin into a heated corebox where it is allowed to harden into a workable foundry shape and then removed from the corebox.
The bench life of the foundry mix is the time period between forming the mixture of the aggregate and binder and the time when the mixture is no longer useful for making acceptable molds and cores. A measure of mold and core acceptability is tensile strength. If a foundry mix consisting of aggregate and binder composition is used after the bench life has expired, the resulting molds and cores will have insufficient tensile strength.
Since the foundry mix of a hot-box system consists of an aggregate containing a latent acid curing catalyst and a thermosetting resin, the catalyst and resin may react prior to shaping the mix into foundry molds and cores. If this reaction occurs, it will reduce the flowability of the foundry mix and the resulting molds and cores will have reduced strength. Additionally, it will be necessary to clean the hoppers, in which the foundry mix is stored, more frequently. This is time consuming and expensive.
Without a benchlife extender, it is difficult to store a hot-box foundry mix for even two hours before using it. Because is not always possible to use the foundry mixes immediately after mixing, it is desirable to prepare foundry mixes with an extended bench life.